From a sort-of related metalink on Oracle which says :
Although the problem couldn't be recreated by the development team on demand, from the exception is clear that the root cause of the problem is the differnce of the version of the org.eclipse.persistence jar distributed with Oracle JDeveloper and Oracle WLS.
I figured this was something to do with the version of eclipselink libraries currently running on the soa server were different from Jdeveloper install.
In my JDeveloper project, I had some libraries and classpath pointing to my JDeveloper install and some others pointing to my SOA middleware home install for example. Read the complete article here.
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